os: add Seek whence constants

R=r, r2, rsc1, rsc, jacek.masiulaniec
CC=golang-dev
https://golang.org/cl/4344062

src/pkg/archive/tar/reader.go

@@ -95,7 +95,7 @@ func (tr *Reader) skipUnread() {
 	nr := tr.nb + tr.pad // number of bytes to skip
 	tr.nb, tr.pad = 0, 0
 	if sr, ok := tr.r.(io.Seeker); ok {
-		if _, err := sr.Seek(nr, 1); err == nil {
+		if _, err := sr.Seek(nr, os.SEEK_CUR); err == nil {
 			return
 		}
 	}

src/pkg/archive/zip/reader.go

@@ -73,7 +73,7 @@ func NewReader(r io.ReaderAt, size int64) (*Reader, os.Error) {
 		Comment: end.comment,
 	}
 	rs := io.NewSectionReader(r, 0, size)
-	if _, err = rs.Seek(int64(end.directoryOffset), 0); err != nil {
+	if _, err = rs.Seek(int64(end.directoryOffset), os.SEEK_SET); err != nil {
 		return nil, err
 	}
 	buf := bufio.NewReader(rs)
@@ -94,7 +94,7 @@ func (f *File) Open() (rc io.ReadCloser, err os.Error) {
 		if err = readFileHeader(f, r); err != nil {
 			return
 		}
-		if f.bodyOffset, err = r.Seek(0, 1); err != nil {
+		if f.bodyOffset, err = r.Seek(0, os.SEEK_CUR); err != nil {
 			return
 		}
 	}

src/pkg/debug/elf/file.go

@@ -228,7 +228,7 @@ func NewFile(r io.ReaderAt) (*File, os.Error) {
 	switch f.Class {
 	case ELFCLASS32:
 		hdr := new(Header32)
-		sr.Seek(0, 0)
+		sr.Seek(0, os.SEEK_SET)
 		if err := binary.Read(sr, f.ByteOrder, hdr); err != nil {
 			return nil, err
 		}
@@ -243,7 +243,7 @@ func NewFile(r io.ReaderAt) (*File, os.Error) {
 		shstrndx = int(hdr.Shstrndx)
 	case ELFCLASS64:
 		hdr := new(Header64)
-		sr.Seek(0, 0)
+		sr.Seek(0, os.SEEK_SET)
 		if err := binary.Read(sr, f.ByteOrder, hdr); err != nil {
 			return nil, err
 		}
@@ -269,7 +269,7 @@ func NewFile(r io.ReaderAt) (*File, os.Error) {
 	names := make([]uint32, shnum)
 	for i := 0; i < shnum; i++ {
 		off := shoff + int64(i)*int64(shentsize)
-		sr.Seek(off, 0)
+		sr.Seek(off, os.SEEK_SET)
 		s := new(Section)
 		switch f.Class {
 		case ELFCLASS32:

src/pkg/debug/pe/file.go

@@ -132,7 +132,7 @@ func NewFile(r io.ReaderAt) (*File, os.Error) {
 	} else {
 		base = int64(0)
 	}
-	sr.Seek(base, 0)
+	sr.Seek(base, os.SEEK_SET)
 	if err := binary.Read(sr, binary.LittleEndian, &f.FileHeader); err != nil {
 		return nil, err
 	}
@@ -140,7 +140,7 @@ func NewFile(r io.ReaderAt) (*File, os.Error) {
 		return nil, os.NewError("Invalid PE File Format.")
 	}
 	// get symbol string table
-	sr.Seek(int64(f.FileHeader.PointerToSymbolTable+18*f.FileHeader.NumberOfSymbols), 0)
+	sr.Seek(int64(f.FileHeader.PointerToSymbolTable+18*f.FileHeader.NumberOfSymbols), os.SEEK_SET)
 	var l uint32
 	if err := binary.Read(sr, binary.LittleEndian, &l); err != nil {
 		return nil, err
@@ -149,9 +149,9 @@ func NewFile(r io.ReaderAt) (*File, os.Error) {
 	if _, err := r.ReadAt(ss, int64(f.FileHeader.PointerToSymbolTable+18*f.FileHeader.NumberOfSymbols)); err != nil {
 		return nil, err
 	}
-	sr.Seek(base, 0)
+	sr.Seek(base, os.SEEK_SET)
 	binary.Read(sr, binary.LittleEndian, &f.FileHeader)
-	sr.Seek(int64(f.FileHeader.SizeOfOptionalHeader), 1) //Skip OptionalHeader
+	sr.Seek(int64(f.FileHeader.SizeOfOptionalHeader), os.SEEK_CUR) //Skip OptionalHeader
 	f.Sections = make([]*Section, f.FileHeader.NumberOfSections)
 	for i := 0; i < int(f.FileHeader.NumberOfSections); i++ {
 		sh := new(SectionHeader32)

src/pkg/http/fs.go

@@ -148,7 +148,7 @@ func serveFile(w ResponseWriter, r *Request, name string, redirect bool) {
 		} else {
 			w.Header().Set("Content-Type", "application/octet-stream") // generic binary
 		}
-		f.Seek(0, 0) // rewind to output whole file
+		f.Seek(0, os.SEEK_SET) // rewind to output whole file
 	}
 
 	// handle Content-Range header.
@@ -163,7 +163,7 @@ func serveFile(w ResponseWriter, r *Request, name string, redirect bool) {
 	}
 	if len(ranges) == 1 {
 		ra := ranges[0]
-		if _, err := f.Seek(ra.start, 0); err != nil {
+		if _, err := f.Seek(ra.start, os.SEEK_SET); err != nil {
 			Error(w, err.String(), StatusRequestedRangeNotSatisfiable)
 			return
 		}

src/pkg/os/file.go

@@ -61,6 +61,13 @@ const (
 	O_CREATE   int = O_CREAT            // create a new file if none exists.
 )
 
+// Seek whence values.
+const (
+	SEEK_SET int = 0 // seek relative to the origin of the file
+	SEEK_CUR int = 1 // seek relative to the current offset
+	SEEK_END int = 2 // seek relative to the end
+)
+
 type eofError int
 
 func (eofError) String() string { return "EOF" }